Adjustable rotary slip clutches are known to be generally comprised of two members, i.e. a driving member and a driven member, which are operable to engage each other at an adjustable pressure such that the driven member follows the driving member by means of friction. When the load on the driven member becomes excessively high, the clutch slips and the driven member comes to a standstill. Such clutches generally include friction pads operable to engage each other along planar surfaces to provide the friction engagement between the two members. Such clutches are typically applicable for transmitting relatively large loads and generally operate at relatively high speed settings.
Such clutches, however, are generally not suitable for applications requiring accurate transmission of very small loads and are not capable of small incremental adjustments. In this respect, the friction elements typically found in such devices are simply not suitable or operable in certain low speed applications where relatively low torque loads are to be transmitted or where the friction contact between the friction elements must be accurately and incrementally adjustable for very low torque loads.
For example, in a copper foil treatment line, a large continuous sheet of metallic foil is conveyed over a plurality of rollers into various treatment baths. Such rollers are generally driven by gears connected to a timing chain to provide a uniform drive along the length of foil. In such a production line, it is critical that the rollers be timed to move in sequence with the foil conveyed thereon, in that the smallest deviations in roller speed relative to the foil speed can produce scratching and scuffing of the metallic foil thereby affecting its quality and value. Even with the most accurate timing chain and gear assemblies, however, successive rollers cannot be precisely timed. In this respect, even the smallest misalignment or misspacing will produce a slight error between the movement of the drive chain and the rotation of the gear and roller, which error accumulates over each revolution of the gear until the gear and roller accelerate or decelerate to correct itself thereby producing a scratch or mark on the foil being conveyed. When it is considered that rollers in a typical foil treatment line may rotate at less than thirty (30) revolutions per minute (r.p.m.), typically 2-20 r.p.m., it becomes apparent that rotary slip clutches known heretofore are not suitable in such low speed, low torque transmission settings.
The present invention overcomes these problems and provides a relatively simple rotary slip clutch which is capable of adjustment between extremely small transmission loads and extremely large transmission loads yet which is adjustable in extremely small increments, especially at low transmission torque settings.